The present invention relates to the general field of cooling the disks of high-pressure and low-pressure turbines in a turbomachine. The invention relates more particularly to a device for cooling the disk of moving blades of the high-pressure turbine and the disks of rotary blades of the low-pressure turbine in a turbomachine.
In a turbomachine, the disks of the high- and low-pressure turbines are generally cooled by injecting air coming from the nozzle of the low-pressure turbine via annular plates mounted under the bottom platform supporting fixed vanes of the nozzle. FIG. 7 is a diagram of the junction between the high- and low-pressure turbines of a turbomachine with a cooling device of known type. In this figure, three annular plates 100 are fixed to a bottom platform 102 for supporting a fixed vane 104 of the nozzle 106 of the low-pressure turbine. Assembled together, these plates create an annular cavity 108 fed with cooling air via link bushings 110 collecting the air that comes from the base of the fixed vane 104 of the nozzle. Holes 112 formed through the plate 100 serve to inject the cooling air towards a disk 114 for the moving blades 116 of the high-pressure turbine and a disk 118 for the rotary blades 120 of the low pressure turbine. A fourth annular plate 122 extends radially between the three assembled-together plates 100 and a flange 124 on the disk 114 for the moving blades, enabling the assembly to define a high-pressure enclosure 126 and a low-pressure enclosure 128.
The quality of cooling applied to the disks of the high- and low-pressure turbines depends in particular on the feed of cooling air from the injection cavity defined by the annular plate of the cooling device. In particular, it is important to obtain good leaktightness for said cavity and to avoid head losses in its feed. Head losses are generally the result of poor quality air flow at the outlet from the link bushings. In the cooling device shown in FIG. 7, the air flow coming from the link bushings 110 is subjected to a large change of direction (as represented by arrow 130) which gives rise to head losses that are harmful for good operation of the device.
The head losses due to changes in the flow direction of the air feeding such cooling devices are also considerably more marked when the nozzle of the low-pressure turbine is a so-called “swan-necked” nozzle. A swan-neck nozzle is characterized by bottom and top platforms for supporting the fixed vanes that are elongated so as to increase the aerodynamic performance of the low-pressure turbine. Under such circumstances, the plates of the turbine disk cooling device are bent so as to adapt to the elongate shape of the bottom platform of the nozzle so that the cooling air coming from the bases of the fixed vanes is subjected to large changes of direction. As a result, head losses are high at the bends in the plates.